Image quality of a color electrophotographic apparatus such as a copying apparatus or a printer has been progressed, and color reproduction by Japan Color 2003 as a standard color reproduction in the printing area color has been attained by a part of them.
However, color reproduction region in an image composed of each color toner of yellow, magenta and cyan does not cover color reproduction region on computer display screen completely. The technical barrier is caused by the difference of principal that while computer display screen is observed via additive color process by transmitted light, image formed via an electrophotography using color toners is observed via subtractive color process by reflected light. In particular, cyan colorants are restricted in its selection for demand of discoloration image storage property in an electrophotographic apparatus for office use in majority.
A copper phthalocyanine compound having copper in the center metal has been practically used as a cyan colorant, and the copper phthalocyanine compound was excellent in coloring characteristics of low brightness color in cyan region (deep and dark color), however coloring characteristics of high brightness color in cyan region (pale and bright color) was not sufficient.
For the purpose of improving the problem, Patent Document 1, for example, discloses cyan colorants containing phthalocyanine compound in which a substituent is bonded to a center metal atom, and the cyan colorants give a cyan toner for developing an electrostatic image having high brightness and good color tone in color cyan region.
Further technique using two or more compounds in combination has been provided to enhance the color reproduction property of both low brightness color in cyan region and high brightness color in cyan region.
For example, Patent Document 2 discloses a cyan pigment obtained by pulverizing copper phthalocyanine compound and nickel phthalocyanine compound in a wet state in a presence of inorganic salts and organic solvent, and high chroma can be obtained by the cyan pigment since it has smaller particle size in comparison with a method pulverizing a copper phthalocyanine compound singly.
Patent Document 3 discloses a cyan colorant containing a phthalocyanine compound in which a substituent is bonded to a center metal atom, and a phthalocyanine compound in which a substituent is not bonded to a center metal atom in a specific ratio.
However, toner exhibiting sufficient color reproduction property in low brightness color in cyan region as well as high brightness color in cyan region was not realized by employing two or more kinds of above described compounds as colorants by the detailed study of the inventor of the present invention.